Since Frank Zappa died in 1993, his music has enjoyed a remarkable posthumous career. His albums are still in print and easily available on CD, but that’s true of John Lennon and Jerry Garcia, too. What makes Zappa unique among the rock stars of his generation is that his work is continually being rearranged, performed and recorded by musicians outside the rock sphere. A search of his name at Amazon.com turns up recent recordings by classical ensembles, big bands and even a Baroque chamber orchestra.

In other words, Zappa is not just an oldie, an object of ’60s nostalgia. He is on his way to becoming a classic in the mold of George Gershwin, another American composer whose music has been mined and adapted by generations of singers and instrumentalists.

Project/Object, which returns to Sellersville Theater 1894 this weekend, adheres more closely to the format Zappa established for his stage shows, particularly those from the late 1970s and early ’80s. André Cholmondeley, guitarist, Zappaphile and driving force behind the group, likes the sound of the stripped-down rock groups — guitars, bass and drums overlaid with some synthesizers and vibraphone — that Zappa employed after his mid-’70s flirtation with big, horn-laden orchestras…